Capacitance Sensor Stuck Mass Detection and Recovery
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Solution Overview
Problem
Capacitance type physical quantity sensors face issues with determining if the mass portion is stuck to the fixed electrode, leading to inaccurate acceleration measurements and a lack of effective countermeasures for abnormal operation detection.
Innovation Solution
A physical quantity sensor with a detection circuit that determines normal or abnormal operation based on signal stability, utilizing a control circuit to store and communicate setting information and apply bias voltages to restore normal operation without forming new electrodes, and an inertial measurement unit incorporating this sensor for posture and momentum detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitance type physical quantity sensor is used to detect acceleration, then detection capability is improved, but when mass portion sticks to fixed electrode the capacitance becomes very large causing inaccurate detection
Solution Approach 1:
The determination circuit proactively monitors the detection signal to identify when the mass portion is stuck to the fixed electrode, and the control circuit preemptively applies a reverse voltage to separate them before permanent damage or extended malfunction occurs. This preliminary detection and correction mechanism prevents the sticking condition from causing permanently inaccurate measurements.
Solution Approach 2:
The system continuously monitors the detection signal output from the physical quantity detection element and feeds this information back to the determination circuit. When the signal indicates abnormal capacitance values consistent with sticking, the feedback loop triggers the control circuit to apply corrective reverse voltage, creating a closed-loop system that automatically corrects detection errors.
2Ease of repair
If electrode is added to peel mass portion from fixed electrode, then device complexity increases, but without it the sensor cannot recover from sticking
Solution Approach 1:
The control circuit serves multiple functions: it normally drives the physical quantity detection element during operation, monitors detection signals through the determination circuit, and switches to applying reverse voltage for separation when sticking is detected. By making the control circuit multi-functional, the patent avoids adding separate dedicated electrodes or complex additional hardware while still providing effective recovery capability.
Solution Approach 2:
The system uses its own existing electrical components and power supply to perform the separation function. The control circuit utilizes the existing voltage supply infrastructure to apply reverse voltage, and the determination circuit uses the existing detection signal path to identify sticking conditions. This self-service approach eliminates the need for external electrodes or additional complex mechanisms.
3Reliability
If no determination mechanism is added, then device complexity remains low, but the sensor cannot detect abnormal operation state
Solution Approach 1:
The determination function is merged into the existing control circuit rather than being implemented as a separate dedicated subsystem. The control circuit combines normal operation control, signal monitoring, abnormality determination, and corrective action in a single integrated unit. This merging approach provides reliable abnormal operation detection while minimizing the increase in device complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables detection and correction of abnormal sensor operations, ensuring accurate measurements and extending sensor lifespan without requiring new electrode formation, thus enhancing reliability and usability in inertial measurement applications.
Implementation Method 1
capacitance type physical quantity sensors have been developed that detect a physical quantity by using the fact that a value of capacitance generated between opposing electrodes provided in a physical quantity detection element changes with the magnitude and direction of the physical quantity such as acceleration and angular velocity
Implementation Method 2
a determination circuit that determines whether a value of the physical quantity signal continuously remains within a predetermined range in a predetermined period
Data Source
AI summary
A physical quantity sensor includes a physical quantity detection circuit having a determination circuit that determines whether a value of a physical quantity signal continuously remains within a predetermined range in a predetermined period, determines that a physical quantity detection element is in a first state of normal operation when the value does not continuously remain, and determines that the physical quantity detection element is in a second state of abnormal operation when the value continuously remains, a control circuit that stores first information based on a determination result of the determination circuit is stored in a control circuit as a setting information and a communication section that outputs the setting information stored in from the control circuit to the outside when the determination result of the determination circuit indicates the second state.